<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>20个圆</title>
    <style>
      
	.yibaige{
		width: 580px;
		
	}
	.circle{
		width: 60px;
		height: 60px;

		margin: 2px;
		display: inline-block;
		border-radius: 50%;
		border:2px green solid;
		text-align: center;
		line-height: 60px;
		color: white
	}
	.circle:nth-child(2n){
		background-color: rgb(84, 181, 103);
	}
	.circle:nth-child(2n+1){
		background-color: rgb(42, 31, 238);
	}
	

    </style>
</head>
<body>
    <div class="yibaige">
        <div class="circle">
            <div>
                <span>1</span>
            </div>
        </div>
        <div class="circle">
            <div>
                <span>2</span>
            </div>
        </div>
        <div class="circle">
            <div>
                <span>3</span>
            </div>
        </div>
        <div class="circle">
            <div>
                <span>4</span>
            </div>
        </div>
        <div class="circle">
            <div>
                <span>5</span>
            </div>
        </div>
        <div class="circle">
            <div>
                <span>6</span>
            </div>
        </div>
        <div class="circle">
            <div>
                <span>7</span>
            </div>
        </div>
        <div class="circle">
            <div>
                <span>8</span>
            </div>
        </div>
        <div class="circle">
            <div>
                <span>9</span>
            </div>
        </div>
        <div class="circle">
            <div>
                <span>10</span>
            </div>
        </div>
        <div class="circle">
            <div>
                <span>11</span>
            </div>
        </div>
        <div class="circle">
            <div>
                <span>12</span>
            </div>
        </div>
        <div class="circle">
            <div>
                <span>13</span>
            </div>
        </div>
        <div class="circle">
            <div>
                <span>14</span>
            </div>
        </div>
        <div class="circle">
            <div>
                <span>15</span>
            </div>
        </div>
        <div class="circle">
            <div>
                <span>16</span>
            </div>
        </div>
        <div class="circle">
            <div>
                <span>17</span>
            </div>
        </div>
        <div class="circle">
            <div>
                <span>18</span>
            </div>
        </div>
        <div class="circle">
            <div>
                <span>19</span>
            </div>
        </div>
        <div class="circle">
            <div>
                <span>20</span>
            </div>
        </div>
        <div class="circle">
            <div>
                <span>21</span>
            </div>
        </div>
    </div>
    
    

    
</body>
</html>